/**
   * @fileoverview Rule to enforce spacing around embedded expressions of template strings
   * @author Toru Nagashima
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Requirements
  //------------------------------------------------------------------------------
  
  const astUtils = require("../ast-utils");
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  const OPEN_PAREN = /\$\{$/;
  const CLOSE_PAREN = /^\}/;
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = {
      meta: {
          docs: {
              description: "require or disallow spacing around embedded expressions of template strings",
              category: "ECMAScript 6",
              recommended: false
          },
  
          fixable: "whitespace",
  
          schema: [
              { enum: ["always", "never"] }
          ]
      },
  
      create(context) {
          const sourceCode = context.getSourceCode();
          const always = context.options[0] === "always";
          const prefix = always ? "Expected" : "Unexpected";
  
          /**
           * Checks spacing before `}` of a given token.
           * @param {Token} token - A token to check. This is a Template token.
           * @returns {void}
           */
          function checkSpacingBefore(token) {
              const prevToken = sourceCode.getTokenBefore(token);
  
              if (prevToken &&
                  CLOSE_PAREN.test(token.value) &&
                  astUtils.isTokenOnSameLine(prevToken, token) &&
                  sourceCode.isSpaceBetweenTokens(prevToken, token) !== always
              ) {
                  context.report({
                      loc: token.loc.start,
                      message: "{{prefix}} space(s) before '}'.",
                      data: {
                          prefix
                      },
                      fix(fixer) {
                          if (always) {
                              return fixer.insertTextBefore(token, " ");
                          }
                          return fixer.removeRange([
                              prevToken.range[1],
                              token.range[0]
                          ]);
                      }
                  });
              }
          }
  
          /**
           * Checks spacing after `${` of a given token.
           * @param {Token} token - A token to check. This is a Template token.
           * @returns {void}
           */
          function checkSpacingAfter(token) {
              const nextToken = sourceCode.getTokenAfter(token);
  
              if (nextToken &&
                  OPEN_PAREN.test(token.value) &&
                  astUtils.isTokenOnSameLine(token, nextToken) &&
                  sourceCode.isSpaceBetweenTokens(token, nextToken) !== always
              ) {
                  context.report({
                      loc: {
                          line: token.loc.end.line,
                          column: token.loc.end.column - 2
                      },
                      message: "{{prefix}} space(s) after '${'.",
                      data: {
                          prefix
                      },
                      fix(fixer) {
                          if (always) {
                              return fixer.insertTextAfter(token, " ");
                          }
                          return fixer.removeRange([
                              token.range[1],
                              nextToken.range[0]
                          ]);
                      }
                  });
              }
          }
  
          return {
              TemplateElement(node) {
                  const token = sourceCode.getFirstToken(node);
  
                  checkSpacingBefore(token);
                  checkSpacingAfter(token);
              }
          };
      }
  };